drm/i915: Add intel_bios_cleanup() function

Add an intel_bios_cleanup() function to act as counterpart of
intel_bios_init() and move the cleanup of vbt related resources there,
putting it in the same file as the allocation.

Changed in v2:
-While touching the code anyways, remove the unnecessary:
 if (dev_priv->vbt.child_dev) done before kfree(dev_priv->vbt.child_dev)

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180214082151.25015-1-hdegoede@redhat.com
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 8bd55b5..0c0a402 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -3679,6 +3679,7 @@ extern void intel_i2c_reset(struct drm_i915_private *dev_priv);
 
 /* intel_bios.c */
 void intel_bios_init(struct drm_i915_private *dev_priv);
+void intel_bios_cleanup(struct drm_i915_private *dev_priv);
 bool intel_bios_is_valid_vbt(const void *buf, size_t size);
 bool intel_bios_is_tv_present(struct drm_i915_private *dev_priv);
 bool intel_bios_is_lvds_present(struct drm_i915_private *dev_priv, u8 *i2c_pin);